Some have argued, for example, that the geometric visual hallucinations commonly seen by people on psychedelics (and by some sufferers of migraines) help reveal the architecture of the brain’s visual processing mechanism. “One hypothesis is that what you’re actually seeing is the functional organization of the visual cortex itself. The visual cortex is organized in a sort of fractal way [it repeats the same patterns in different sizes]. It’s the same way that fractals are everywhere in nature. Like tree branches, the brain recapitulates [itself],” says Carhart-Harris. “You’re not seeing the cells themselves, but the way they’re organized — as if the brain is revealing itself to itself.”